The present invention involves an improved chopper for chopping continuous or very long fiber, fiber strands, yarn, string, wire, ribbon, tape and the like comprising a backup roll and a blade roll. More specifically, the present invention involves a chopper having a novel quick release knock off-knock on roll retainer for the rolls that must be frequently changed, and means for tilting the chopper to change the angle of discharge of the chopped strand, etc.
It has long been known how to chop continuous fibers or fiber strands into short lengths of about 3 inches or shorter. More than a billion pounds of such products including chopped glass fibers and fiber strands are produced each year in processes and chopping apparatus like those disclosed in U.S. Pat. Nos. 5,970,837; 4,398,934; 3,508,461; and 3,869,268. The choppers disclosed in these patents comprise a blade roll containing a plurality of spaced-apart blades for separating the fibers into short lengths, a backup roll, frequently driven, which the blades work against to effect the separation and which pulls the fibers or fiber strands, often using an idler roll to hold the fibers or fiber strands down onto the surface of the backup roll. In the chopped fiber processes disclosed in these patents, the chopper is usually the most productivity limiting equipment in the processes that typically operate continuously every day of the year, 24 hours each day. Therefore, improvements in the chopper that allow the chopper to pull and chop faster, allow longer times between maintenance shutdowns, and/or to pull and chop more fibers or fiber strands at a time have an extremely positive impact on productivity and production costs.
Due to wear, the blade roll and backup roll on each chopper must be changed frequently with the actual life between changes depending upon the type of item being chopped. The life typically ranges between 4 and 24 hours or more, but a defect in a blade or the elastomer layer on the backup roll can cause even shorter life. Due to their tightness on their spindles and the tacky chemical sizing from the fiber that gets on all exposed parts, it has been necessary to strike the old blade rolls and old backup rolls with a hammer or a heavy bar to loosen them from their spindles before they could be removed for replacement with new rolls. This hammering damages the rolls and in time knocks them out of alignment causing vibration and premature replacement. These are expensive problems for the industry considering that there are hundreds of fiber choppers in operation.
Another problem with fiber choppers when chopping wet fiber having a tacky chemical sizing on the surface of the fibers is that the stream of fibers will, depending on factors such as moisture content and the degree of tackiness of the sizing, leave the chopper at different angles. This presents a problem in catching the fiber with a conveyor belt due to the limited space in the fiber forming rooms where the fiber is formed and chopped and results in some fiber being thrown off the conveyor and onto the floor causing scrap and a housekeeping problem. This problem is discussed in U.S. Pat. No. 4,161,897 and the problem is addressed in that patent by designing the chopper such that the position of the blade roll can be changed to contact the backup roll in different locations. While this may change the angle of discharge of the chopped fiber, it greatly complicates the design and is a costly solution. A simpler, less costly solution has been needed.